Fire extinguisher



Nov. 18, 1952 c, MacDONALD 2,618,347

FIRE EXTINGUISHEZR Filed March 29, 1946 2 SHEETS-SHEET 1 f: 5 "5T1".-nfj I 15;:11'.

INVEN TOR.

Nov. 18, 1952 c. MHCDONALD FIRE sx'rmcursmaa 2 SHEETSSHEET 2 Filed March29, 1946 Patented Nov. 18, i952 UNITED STATES PATENT OFFICE Claims.

This invention relates to fire extinguishing devices and moreparticularly to an improved means for producing atomization or foggingof fire extinguishing mediums and for projecting the same.

Present practice in producing water fog for fire fighting purposesemploys a high pressure pump, usually engine driven from the fire truck,and apparatus which produces fog by the angular impingement of highpressure streams of water and by the action of suitable deflecting vanesor nozzles. Such a construction requires a relatively heavy highcapacity driven pump together with high pressure hose, etc., forapplication.

. It is an object of my invention to provide a compact and easilyportable means for attaining the atomization of water or other fireextinguishing fluids with the further advantage of admixing with theprojected fog entrapped gases which do not foster combustion, incontradistinction to the fanning effect often produced by conventionalfog extinguishers due to a nonhomogeneous fog projection and to theentrapment of air in the moving fog.

A further object of this invention is to provide means resulting ingreater projection distance of the fire-extinguishing fog with aconsequent increase in the utility and safety of the improved device.

My invention secures the object advantages stated above by employinggases generated from the combustion of a suitable propellant, usually asolid, to atomize and project a fog-like fireextinguishing medium, asdistinguished from present systems employing purely mechanicalproduction of fog and from those systems employing a compressed gas,such as carbon dioxide, as the fog producing agent. It will be seen fromthe following description that my system for producing and projectingfog has many advantages, such as maximum portability in that powerdriven high-pressure pumps are not required, high safety in that it doesnot employ a separate or integral storage vessel for bottled gases underpressure, and excellent efiiciency in that it provides for a maximum ofgas generation in a minimum .of storage space, thus insuring most fluidvolume in a given size extinguisher. Other advantages of my fireextinguishing system are that the device does not have to be checked forgas pressure as is the case when compressed gases areused, the devicemay be easily serviced, in that additional prepared propellantcartridges may be inserted with no more difliculty than in reloading theconventional soda and acid type fire extinguisher, and the device mayprovide a tremendous rate of discharge of fog if desired, by merelyincreasing the size of the propellant grain and fog-producing nozzle orplay pipe, This latter advantage is of special value in in dustrial andairport use where extremely high discharge rates are required for arelatively short time and where portability and ease of servicing areparamount in importance.

Other objects and advantages of the invention will be apparent duringthe course of the following description, reference being made to theattached drawing wherein:

Figure 1 is a vertical section view of the top portion of a small,portable fog fire extinguisher, intended for the same general usage asthe common 2 gallon soda and acid extinguisher now in extensive use.

Figure 2 is a vertical section view of my fogproducing device forapplication to a standard fire hose, whereby a fog producing nozzle isemployed in place of the customary play pipe.

Referring to the drawings for the purpose of illustration, Figure 1depicts a cross section through an extinguisher of the portable typeshown prior to initiating operation. Ignition of the propellant grain lI, continued in the powder chamber l2 produces a rapid evolution ofgases within the interior of cover l3. The propellant grain may be anywell known combustiblematerial, such, for example, as rocket-typepropellants composed of approximately equal amounts of nitrocelluloseand nitroglycerin with small amounts of additives. One such propellantis described in United States Patent 1,923,849,

issued to Stickland and Stevenson on August 22, 1933, and comprisesfifty parts nitrocellulose, forty-one parts nitroglycerine, plus nineparts of diethyldiphenylurea and phenyl urethane. -A propellant grainweighing of the order of one pound is'adequate to project the fogproduced from two to five gallons of fire extinguishing medium. Thegaseous products of combustion issue through the throat (narrowestportion): of nozzle I i at the local velocity of sound. 3,500 feet persecond may be considered to'be' a representative throat velocity withmodern solid propellants and this velocity may be greatly-increased byexpanding (as in supersonic-.wind tunnels) through the divergent portionof the nozzle.

-This high speed gas jet siphons thelwater or other fire extinguishingmedium up the 'annular passage I5, between the siphon tube 16 and thepropellant chamber l2, The mechanical mixture of combustion gases andwater or other fire extinguishing medium thus formed in the mixing zoneof the nozzle l8 produces a finely divided fog which is projected out ofthe nozzle in the direction indicated by the arrow IS. The outer shellor reservoir of the extinguisher is indicated by the numeral I1, and acheck or relief valve 20 permits the admission of air into the reservoirH as liquid is siphoned up the tube 6.

The ignition system whereby combustion of the propellant grain l l isinitiated may be either by electrical means as is current practice inthe rocket art or may be by percussion, mechanically actuated, as iscommon practice in artillery and small arms constructions. For example,a conventional rocket propellant igniter is shown in Figures 1 and 2 inthe form of a silk bag .33 containing a few grains of black powder andan electric squib connected to lead wires 34 extending out through thenozzles for connection to a conventional battery and switch.

- A safety groove 2| may be employed to insure against generation ofexcessive pressures within the combustion chamber l2. Such a groove maybe designed to fail at any desired pressure and upon separation willresult in increasing the available gas exit area to such an extent thatthe propellant will then be extinguished. This construction is commonpractice in the rocket art.

Figure 2 depicts an installation intended for high rates of dischargeand intended as a fogproducing adjunct to be coupled directly to firehose lines. This may be considered as representative of either a playpipe which is attached to the delivery end of a fire hose and used todirect the discharge therefrom, or a branch supply pipe which forms partof a fixed system. Ignition of propellant grain 22 by any of the severalapplicable means produces an evolution of gas inside the powder chamber23 which is closed by the quick acting breech mechanism 24. The gases sogenerated are directed through the nozzle 25 and produce a rearwardthrust sliding the nozzle assembly 26 rearward against stop 21, thenozzle assembly 23 being slidably secured to the inlet casting 28. Thisaction opens the valve ports 32 between the inlet casting 28 and thenozzle assembly 26, permitting water from the fire hose, attached tothreads 29, to flow through the inlet casting and into the areasurrounding the powder chamber 23. The fog of water and gases thusproduced in the mixing zone '30 issues from the nozzle in the directionshown'by the arrow 3|.

Not shown are the means employed for ignition of the powder grain, thehandles for manually directing the nozzle or play pipe and the springrecoil mechanism whereby nozzle assembly 26 is returned to a positionpermitting no water flow when combustion of the propellant, with itsattendant rearward reaction, ceases.

It will be understood that the scope of this invention is not limited tothe exemplary structure illustrated and specifically described, but islimited only by the scope of the following claims.

I claim:

1. In a fire extinguisher for use with a hose supplying a liquid fireextinguishing medium, the combination comprising an inlet connection forsaid medium, a combustion chamber slidably carried by said inletconnection, a mixing chamber carried by said combustion chamber, saidmixing chamber having an outlet nozzle connected thereto, and valvemeans operable by sliding movement of said mixing chamber to an openposition admitting the flow of said medium from said inlet connectioninto said mixing chamber.

2. In a fire extinguisher, the combination comprising a container for afiuid fire-extinguishing medium, a combustion chamber supported by saidcontainer and adapted to contain a combustible propellant, means forigniting a combustible propellant within said chamber, means defining anoutlet nozzle connected to said chamber, and means defining a passagesurrounding said outlet nozzle and communicating with said container foradmitting said fluid fire-extinguishing medium into the combustionproducts emitted from said nozzle.

3. In a fire extinguisher, the combination comprising a container for afluid fire-extinguishing medium, a combustion chamber supported by saidcontainer and adapted to contain a combustible propellant, means forigniting a combustible propellant within said chamber, means defining anoutlet nozzle connected to said chamber, a second chamber surroundingsaid nozzle and communicating with said container for ad mitting saidfluid fire-extinguishing medium into combustion products emitted fromsaid nozzle,

and means defining a second nozzle connected to said second chamber andcoaxial with saidfirst nozzle for directing a stream of mixed combustionproducts and fire-extinguishing medium.

4. In a fire extinguisher, the combination comprising, a container for afluid fire-extinguishing medium, a combustion chamber supported by saidcontainer and adapted to contain a combustible propellant, an igniterfor igniting a combustible propellant within said chamber, meansdefining an outlet nozzle connected to said chamber, means defining achamber surrounding said nozzle, a siphon passage. connecting said lastchamber with said container, and an outlet nozzle for said last chamberfor directing a stream of mixed combustion products andfireextinguishing medium.

5. The method of producing a stream of fire extinguishing fog whichcomprises the steps of igniting a combustible propellant within achamber having an outlet nozzle, forming by said nozzle a high velocitystream of the gaseous products of the combustion of said propellant, andintroducing said high velocity stream of combustion products a fluidfire-extinguishing medium, whereby said fire-extinguishing medium isdrawn into and mixed with said combustion productsto form a stream offire-extinguishing fog.

GILMOUR C. MACDONALD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 405,717 Rew June 25, 1889 690,633Brigham 1 Jan. 7, 1902 779,923 Gillett Jan. 10, 1905 1,774,952 ThieckeSept. 2, 1930 2,115,442 Emery Apr. 26, 1938 2,338,313 Bishop -1 Jan.'4,.1944.

